This invention relates to the field of assembly line production. More specifically, the invention relates to the efficient transport of automobiles in assembly line manufacturing operations.
Assembly lines require vehicles to be transported, making them pass through a series of work stations in which different elements or components are added.
Depending on the elements to be added at each station, it may be convenient for the vehicle to have a more or less elevated height, which is achieved by means of a suitable transport device.
These transport devices have an elevated rail on which a carriage is mounted which moves longitudinally along the rail, transporting the vehicle in a longitudinal direction through the different work stations. From this carriage, a series of elements are suspended which enable the height of the vehicle to be varied with respect to the floor, which generally includes an upper frame fixed to the carriage, a lower frame provided with arms to hold the vehicle, an elevation mechanism which enables the height of the lower frame with respect to the upper frame, to be varied.
There are several means used to achieve the variable elevation of the vehicle; for example in patent DE 4326563, a vertically-positioned telescopic cylinder is used, which causes lateral stability problems as the vehicle is laterally pushed during the assembly of some of its components.
In patents SU 000220456 and DE 9416172 U, the upper and lower frames are connected by scissor mechanisms, the arms of which are articulated in the middle, thereby adopting a cross shape. In these patents, owing to the turn of the arms in the middle part, the ends of the scissors that are joined to the lower frame and to the upper frame must have a fixed turning point in one of the arms, and on the other arm, must have means to move with respect to the corresponding frame. Because of the shape of the scissor mechanism, when it is opened or closed, the arm ends move together or further apart.
The need for one of the scissor ends to move with respect to the upper and lower frames, means that the coupling between them must have a certain tolerance, which causes wear to the mobile parts and the possibility of the lower frame swinging with respect to the upper frame.
Another problem usually occurring in current transport devices used in assembly lines, is the transmission of lateral strength to the upper rail when the elevation unit of the vehicle swings sideways as a result of possible sideway movements of the vehicle.
This invention refers to a perfected device to transport vehicles in assembly lines, this device being of a type which includes: a lifted rail on which a moving carriage is assembled, an upper frame suspended from the carriage, a lower frame provided with arms to grip the vehicle, a cable elevation mechanism which enables the height of the lower frame with respect to the upper frame, to be varied, and means to stop the lower frame from swinging with respect to the upper frame during assembly.
The device of this invention provides a series of building details with the object of preventing the lower frame from swinging with respect to the upper frame, both in the longitudinal and the transverse directions, and means to stop the elevation unit of the vehicle from balancing with respect to the elevated rail.
The means employed in this device to stop the elevation unit of the vehicle from balancing with respect to the elevated rail, comprises a fixed rail placed parallel to the elevated rail and to one side of the upper frame and includes a side arm joined to the upper frame and provided with support means on the aforementioned fixed rail. The fixed support rail can extend throughout the length of the line, or be placed only in the working areas, as it is precisely in these areas where new components are assembled on the vehicle and, therefore, where it can be pushed sideways.
The support means of the lateral arm, joined to the upper frame, consist of roller elements, which act on the upper and lower sides of the fixed rail, thereby preventing the upper frame from swinging sideways, and therefore, the whole elevation unit of the vehicle with respect to the elevated rail.
The means used to prevent the lower frame from swinging with respect to the upper frame, both in the longitudinal and the transverse directions, consists of four articulated arms, the ends of which are fixed to the frames with horizontal rotation axles.
Each articulated arm consists of an upper bar and a lower bar joined at the opposite ends by means of a horizontal rotation axle. These articulated arms adopt a xe2x80x9cVxe2x80x9d or arm shape and not a double scissor shape as those used in the patents mentioned herein above.
The use of articulated arms provides a series of advantages with respect to the scissor mechanisms, as each is connected to the upper frame and to the lower frame by a single rotation point, which enables greater adjustment in assembly than with the scissors provided by a fixed rotation point and a moving support point.
Two of the four articulated arms which connect the upper to the lower frame, have vertical, parallel planes near to each other, with one of them fixed to one of the sides of the upper frame and the lower frame, and the other to the opposite side of these frames, so that the angles or vertexes defined by these articulated arms are oriented in opposite directions, thereby preventing the lower frame from swinging sideways with respect to the upper frame.
The other two articulated arms are positioned in two parallel, vertical planes, coinciding with the sides of the upper and lower frame, and perpendicular to the two articulated arms mentioned previously.
These two articulated arms are joined by horizontal crossbeams to make them more rigid and ensure that they are parallel, which, together with the two articulated arms mentioned initially, prevents the lower frame from swinging with respect to the upper frame.